Hydraulic system



4 Sheets-Sheet l P. E. SJODIN HYDRAULIC SYSTEM March 15, 1960 Filed Nov. 19, 1957 INVENTOR RES 0 1?/ ATTORNEYS BY i@ M2M P- E. sJoDlN HYDRAULIC SYSTEM March 15, 1960 4 Sheetshee,c 2

Filed Nov. 19, 1957 ATTORNEY5 March 15,. 1960 P. E. sJoDlN 2,928,245

HYDRAULIC SYSTEM Filed Nov. 19, 1957 4 sheets-sheet s M a ,285 zu 279 256 l 8 z 230 24? 27/ 2 5.- 7J' .75. 2 ,1 2S. 5 fzsy@ 7 f 242952 j`z0 256 Z5 254 l INVENTOR E5: q/'odz'n ATTORNE YS March 15, 1960 P. E. s loDlN HYDRAULIC SYSTEM 4 Sheets-Sheet 4 Filed Nov. 19, 1957.,

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INVENTOR ATTORNEY 5 line V11-11 of Figure 9, looking in ,United sata Paten-f HYDRAULIC SYSTEM Peter E. Sjodin, Houston, Tex.

Application November 19, 1957, Serial No. 697,357

s Claims. (Cl. 6o97) The present invention relates to hydraulic systems, and more particularly to hydraulic systems having pressure intensifying means associated therewith.

The primary object of the invention is to provide a hydraulic system in which the pressure responsive means moves rapidly to working position and then moves more slowly with increased power while performing the work operation.

Another object of the invention is to provide a hydraulic system of the class described above in which the pressure responsive device is automatically shifted from fast moving to slow moving operation. v

A further object of the invention is to provide a hydraulic system of the class described above which is inexpensive to manufacture, simple to use, and which is completely eiective in its action.

Other objects and advantages will become apparent in the following specification when considered in thelight of the attached drawings, in which: y

Figure 1 is a vertical cross-section taken through the preferred form of the invention illustrating one position thereof.

Figure 2 is a view similar to Figure 1, illustrating another position of the invention. i

Figure 3 is a view similar to Figure l, illustrating still another position of the invention.

Figure 4 is a transverse cross-section taken along the line 4 4 of Figure l, looking in the direction of the arrows.

Figure 5 is a transverse cross-section taken along the 1ine'5'5 of Figure 3, looking in the direction ofthe arrows.

Figure 6 is a transverse cross-section taken along the line 6 6 of Figure 3, looking in the direction of the arrows.

Figure 7 'is an enlarged fragmentary horizontal cross-v section taken along the line 7-7 of Figure 3, looking in the direction of the arrows.

Figure 8 is a vertical cross-section taken through' al modified form of the invention.

-Figure 9 is a vertical cross-section taken through another modied form of the invention. i' Figure 1() is an'enlarged fragmentary transverse crosssection taken'alongthe line 10-'10 of Figure 9, looking in the direction of the arrows.

Figure 11 is a transverse cross-sectiontaken along the the direction of the arrows.

Figure 12 is a fragmentary transverse cross-section taken along the line 12-12 of Figure 9, looking in the direction of the arrows.

Figure 13 is an enlarged fragmentary horizontal crosssection taken along the line 13-131of Figure 9, lookingA Figure l5 vis an' enlarged fragmentary vertical cross- 2 section taken along the line 15-15 of Figure 14, looking in the direction of the arrows.

Figure 16 is a vertical cross-section taken through another modiied form of the invention.

Figure 17 is a transverse cross-section taken along the line 17,-17 of Figure 16, looking in the direction of the arrows.

Figure 18 is a vertical cross-section taken through another modied form of the invention.

Referring now to the drawings in detail wherein like reference characters indicate like parts through the several gures, and particularly to Figures 1 through 7, wherein the preferred embodiment of the invention is illustrated, lthe reference numeral 20 indicates generally a hydraulic pressure responsive device functioning as a wheel cylinder to press brake shoes 21 and 22 outwardly against a brake drum (not shown).`

The pressure responsive device 20 includes an elongated tubular cylindrical body 23 Ahaving a central partition 24 positioned therein intermediate the opposite ends thereof. Thepartition 24 is formed integrally with the body 23 and has a transversely extending bore 25 extending therein. i

A cylindrical piston 26 is slidably positioned in one end of the tubular body and an identical cylindrical piston 26 is slidably positioned in the opposite end of the body 23. The pistons 26 each have an axial bore 27 extending therein from the outer end thereof. A boss 28 is formed at the inner end of the bore 27 for reasons to be assigned.

The pistons 26, are each provided with a vertically extending slot 29to engage over the free end of the brake shoes 21, 22. The pistons 26 are'previded with an annular groove 30 adjacent the inner ends -thereof in which is positioned a sealing ring 31 ormeii of resilient material.

A cylindrical piston 32 is positioned in the bore 27 for sliding movement therein and has the outer end thereof provided with a vertical slot 33 for engaging over the free ends of the brake shoes 21, 22. The vpiston 32 has an annular groove 34 formed therein adjacent the inner end thereof and having a resilientrsealing ring 3S seated therein.`

A bore 3'6 extends into'the end of the piston'26` op ,posite the bore 27 ata position radially offset with respect to the center of the piston 26. A valve port 37. communicates the bore 27`with the bore 36,y as can be best seen in Figure l.

The piston 32 is limited in its inward movement in the bore 27 by the boss 2S to provide a space between 2'7 and the inner end ofthe normally bias the valve 38 into closed Vposition withV respect to the valve ports 37.

A circular groove 42 is formed on each side of the partition 24 in surrounding relation to the bore y40 and has a sealing 0. ring 43 seated therein for sealing contactv with the inner end of the piston 26 in the area immediately surrounding the bore 36.

Each side of the partition 24 is provided with anannular groove 44 adjacentthe body 23, for reasons to be' assigned. A bore 45 extends between the grooves 44 toprovide communication therebetween. The inner end of 'the bore 25 is provided with a valve seat 46 and has a 3 bore 47 opening therethrough communicating with the bore 45.

A cylindrical valve plug 48 is slidably arranged in the bore 25 and has a shank 49 extending outwardly therefrom. A plug 50 isY threaded into the outerend of the bore 25 and has a vent opening 51 extending therethrough.

A coil spring 52 engages against the valve plug d8V surrounding the shank 49 at one end and has its opposite end engaging against the plug 50 so as to normally urge the valve plug 48 into sealing engagement with the valve seat 46. The valve plug 48 has an annular groove 53 formed therein for holding a sealing O ring 48a in Contact with the walls of the bore 25.

A bore 54 extends perpendicularly from the bore 45 and has its outer end closed by a conventional bleeder valve 55. A bore 56 extends transversely of the bore 25 adjacent the valve seat 46v and has a hydraulic line 57 coupled to the outer. end thereof by a tting 5S.

The inner end portion ofy the valve plug 48 is provided with an annular groove 59 to permit the valve stems 39 to extend into the bore when in their innermost position, as illustrated in Figure 2.

In the use and operation of the invention, as illustrated in Figures l through 7, hydraulic pressure from. a master cylinder (not shown) is exerted through the conduit 57 and hydraulic fluid flows into the bore 56. The lluid in the bore 56 enters the bore 25 and flows outwardly through the bores 40 into the bores 36 and through the valve port 37 into the bores 27.

Hydraulic pressure in the bore 27 moves the piston 32 outwardly in the piston 26 to move the brake shoes 21 and 22 into initial contact with the brake drum (not shown). As the hydraulic pressures increase in the bore 25 due to the increased brake pedal pressure, as well as the cessation of movement of the piston 32, the valve plug 48 is moved rapidly downwardly off of the valve seat 46 aligning the annular groove 59 with the stems 39 of the valves 38 sol that the springs 41 can quickly close the valves 38 trapping the hydraulic fluid in the bore 27 so yas to lock the pistons 32 in their extended position.

After the valve plug 48 has moved away from the seat 46, hydraulic pressure will move through bore 47 which is of restricted size, and outwardly through bore 45 to the annular groove 44 into contact with the inner end of the pistons 26. The pistons 26 having a larger area than the pistons 32 will move the brake shoes 21 and 22 with greatly increased power, but due to' the limited movereit required will use only a small amount of hydraulic On releasing the brake pedal, the shoes 21 and 22 are pulled inwardly by the springs (not shown) forcing the pistons 26 inwardly toward their retracted position. The spring 52 will move the valve plug 48 upwardly in the bore 25 seating in the valve seat 46, and simultaneously moving the groove 59 out of registry with the stems 39 so that as the pistons 26 move inwardly the stems 39 will unseat the valves 38 and release the hydraulic fluid trapped between the piston 32 and the piston 26.

In Figure 8 of the drawings, a modified form of the invention is illustrated, wherein a wheel cylinder 20a is provided for moving a brake shoe 21a outwardly into Contact with a brake drum (not shown). The Wheel cylinder 20a is identical to the wheel cylinder 20 except it is only half as long and contains onlv one large piston 26a at one end thereof with the partition 24a serving also as an end wall.

A small piston 32a isv slidably arranged in the large piston 26a in the same manner as the small piston 32 is slidably arranged in the large piston 26.

The use and operation of the wheel cylinder 20a is identical to that of the wheel cylinder 20 with the exception that a single brake shoe 21a is actuated thereby rather than the two brake shoes 21, 22 of the preferred form of the invention.

Referring now to Figures 9 through 13, a modified form of the invention is illustrated comprising a clamp, indicated generally at 60. The clamp 60 includes a body 61 having a longitudinally extending bore 62 formed in one end thereof, and a longitudinally extending slot 63 formed in the lower edge thereof.

An elongated bar 64 is positioned in the slot 63 and detachably secured therein by bolts 65. The bar 64 extends substantially beyond the body 61 and has an upwardly offset jaw 66 formed integrally on the outer end thereof.

A bore 67 extends transversely into the body 61 perpendicularly to the bore 62 and slightl,I spaced from the inner end thereof. A relatively small bore 68 communicates the bore 67 with the bore 62 at a point adjacent to but spaced from the inner end of the bore 67. The outer` end portion of the bore 67 is provided with a pair of oppositely disposed longitudinally extending slots 69, for reasons to be assigned.

A plug 70 is threaded into the outer end of the bore 67 and has a shaft 71 journalled therein with its outer end projecting beyond the plug 70.

The shaft 71 has a screw driver slot 72 in its outer end and is provided with a collar 73 intermediate its opposite ends and engaging against the plug 7?. The shaft 7i has the end thereof opposite the screw driver slot 72 threaded at 76 from vthe collar 73 to the end.

A plate 75 is positioned in the bore 67 Vand threaded onto the threads 74 of the shaft 71, as can be seen in 1figures 9 and 13. Ears 76 areV integrally formed on the plate 75 engaging in the grooves 69 to restrain the plate 75 against rotation as the' shaft 71 is rotated.

Y A valve seat 77 is formed in the inner end of the bore 67 and has a bore 78 extending axially therefrom. A valveV plug 79 is slidably arranged Vin the bore 67 and is adapted to seat against the valve seat 77 to close the bore 78. The valve plug79'has an annular groove 80 formed therein supporting an elastic sealing O ring 81 for contact with the sides of the bore 67.

A coil spring 82 is positioned between the plate 75 and the valve plug 79 and normally biases the valve plug 79 into engagement with the seat 77. The tension of the coil springr 82` can be adjusted by moving the plate 75 on the shaft 71 through the medium of the threads 74.

Referring now to Figure l0, it can be seen that the valve plug 79. is provided with an annular groove 83, for reasons to be assigned. -A bore 84 communicates with the bore 78 and has the outer end thereof closed by means of'a conventional bleeder valve 85. A here 86 communicates with the bore 67 and has a'hydraulic line 87 connected` to the outer end thereof by a fitting 83.

A circular groove 89 is `formed in the inner end of the bore 62 surrounding the bore 68 and has a sealing O ring 90. positioned therein. An annular groove 91 is formed in the inner end of the bore 62 along the peripheral edges thereof. A bore 93 communicates the bore 73 andthe bore 84 with the annular groove 91.

A cylindrical piston 94 is slidably supported in the bore 62 and has an axial bore 95' extending longitudinally thereof.

A bore 96 is formed in the lower end of the piston 94 in alignment with the bore 68 in the body 61. A valve seat 97 is formed at the inner end of the bore 96 and its juncture with the bore 95.v

A valve 98 is arranged concentrically of the valve seat 97 andhas a stem 99 extending through the bore 96 and into the bore 68. A collar 100 is mounted on the stem 99v and a'coil spring 101 is positioned between the valve seat 97 and the collar 100 to normally bias the valve 98 into engagement with the valve seat 97.

The piston 9;1-'hasl an annular groove 102 formed adjacent the inner end thereofl and an elastic sealing ring 103 is seatedtherein. A cylindrical piston 104 is slidably mounted in the bore 95 and has yan annular groove 105 formed adjacent its inner end supporting anlelastic sealing ring 106. -A boss 107 is-integrally formed at the inner end of the bore 95 to maintain the piston 104 in spaced relation with respect thereto.

A jaw plate 108 has a diameter equal to the piston 94 and is secured to the outer end of the piston 104 by bolts 109. A guide pin 110 is secured to the jaw 108 and is slidably arranged in a bore 111 in the piston 94 spaced from and parallel to the bore 95. The jaw 108 has a depending tongue 112 extending toward the bar 64 and engaging between a pair of upstanding parallel spaced apart plates 113 integrally formed on the upper edge et the bar 64.

The jaw 66 is provided with a socket 114 oppositely of the tongue 112 and a coil spring 115 has one end thereof engaged in the socket 114 vand the opposite end thereof engaging the tongue 112 to normally bias the tongue 1.12 and jaw 108 in 'a direction away from the jaw 66.

In thevuse and operation of the invention illustrated in Figures 9 through 13, hydraulic fluid under pressure ilows through the conduit 87 into the bore 86 and from there into the bore 67. Fluid in the bore 67 iiows outwardly through the bore 68, bore 96, past valve 98 into the bore 95.

When the hydraulic lluid enters the bore 95 it moves the piston 104 quickly outwardly of the bore 95 v to bring the jaw 108 into contact with one side of apiece of work (not shown) engaged between the jaws 66 and 108. When the piston 104 contacts the Work and its movement is retarded, the pressure ofthe hydraulic fluid within the body 61 is increased until it Yovercomes the pressure of the spring 82 forcing the valve plug 79 downwardly in the bore 67 so that the annular groove 83 aligns with the inner end of the stem 99 permitting the valve 98 to close against the seat 97. The closed valve 98 seals thebore 95 and locks the piston 104 in its extended position.

When the valve plug 79 moves downwardly in the bore 67, thebore 78 is opened and iluid flows therethrough and through the bore 93 to the annular groove 91 so that pressure is then brought to bear against the inner end of the piston 94. As the pressure increases in the hydraulic iluid it acts on the larger piston 94 to bring a more intense pressure against the jaw 108 than that exerted by the piston 104. Upon releasing of the pressure on they hydraulic fluid in the system, the coil spring 115 will force the jaw 108 and piston 94 inwardly to return the fluid to a reservoir (not shown). The release of the pressure in thefsystem permits the spring 82 to return the valve plug V79'to engagement with the seat 77 and moves the annular groove 83 out of alignment with the stem 99.

As the piston 94 moves to its innermost position, the stem 99 will contact the valve plug 79 and move the valve 98 off the seat 97 to release the fluid trapped in the bore 95 and permit the piston 104 to move inwardly therein.

'Ihe control of the tension of the spring 82 by means of the'shaft 71 and plate 75 controls the force of the Valve plug 79 against the seat 77 and the counter-acting pressures necessary in the hydraulic vliuid to counteract these pressures.

As can be readily seen, the modification illustrated in Figures 9 through 13, will rapidly move the jaw 108 into contact with the work to be clamped and then will automatically apply a full clamping force without requiring substantial additional hydraulic uid displacement.

Referring now to Figures 1 4 and l5, anothermoditication of the inventionis illustrated and comprises a liftA jack, generally indicated at 116.

The jack 116 includes anupright cylindrical body 117 'having-a `bore 118 extending vdownwardly therethrough `terminating at a point adjacent to butrspaced inwardly from the lower end of the body 117. The inner end 119 of the bore 118 is centrally recessed at `120 and has Aa circulargroove 121 extending downwardly therefrom. An elastic ring seal 122 is seated in the groove 121, for reasons to be assigned.

rA bore 123 extends downwardly from the recess 120 and intersects a bore 124 extending transversely of the body 117 vtoward one side edge thereof. A relatively largeithreaded bore 125 communicates with the outer end of bore'I24 and has a fitting 126 threaded therein and supporting a conduit 127 'in communication with the bore 124.

A generally upright bore 128 is formed in the body 117 adjacent the bore 118 and terminates in a transversely extending threaded bore 129 at the upper end thereof. A.threaded bore 130 extends transversely through the side' of the body 117 intersecting the bore 128 at its inner end. A plug 131 seals the lowerend of the bore 128 below the bore 130, as is shown in Figure 15.

A conduit 132 is secured in communication with the bore 128 by .means .of a tting 133 threadedly engaged in the threaded bore 130. A bore 134 extends axially of the threaded bore 129 and communicates with the bore 118.. A valve ball 135 is arranged in sealing relation to the bore 134 and is normally biased to sealing position by a coil spring 136 supported by a threadedl plug 137 engaged in thethreaded bore 129. j

. A cylindrical piston 138 is mounted for vertical reciprocation in the bore118 and has an axial bore 139 extending from its upper end to a point spaced from but adjacent to its lower end. An annular groove 140 is formed in the piston 138 adjacent the lower end thereof and has an elastic sealing ring 141 seated therein for engagement with the walls of the bore 1 18.

A vent bore 142 extends from the lower edge of the piston 138 to the upper end thereof and is closedat the upper end by a conventional b leeder valve 143. A transverse bore 144 is formed in the piston138 below the inner end of the bore 139. A vented screw plug 145 is threaded into the outer end of the bore 144 and forms a stop for a coil spring 146 positioned in the bore 144.

and adapted to engage against a valve seat 148 formed` in the inner end of the bore 144. The valve plug 147 has a` groove 149 formed annularly thereabout Aand containing an elastic sealing ring 150 for engaging the walls of the bore 144. The valve plug 147 has an annular groove 151 formed adjacent one end-thereof.V

A bore 152 extends axially of the bore 144` terminating at the valve seat 148 atv one end and a bore 153 at the other end. The bore 153 communicates the bore 152 with the bore 139. Y

A threaded bore 154 is formedin the lower end of the piston 138 and has an orifice 155 at its upper end communicating with the bore 144. A threaded hollow bushing 156 is seated in the threaded bore 154 and has a valve seat 157 'formed in its inner end.

A valve 158 having a valve stem 159 depending .therefrom cooperates with the valve seat 157 and is normally biased into engagement therewith by a coil spring 160 engaging the inner end of the hollow bushing 156 at one end and a collar 161 at the other end. l

The stemv159V engages the bottom of thevrecess 120 when the piston 138 is in its lowermost position so that kthe valve 158 is held out of contact with the valve seat 157. The lower end of the threadedbushing 156 engages the seal 122, as can be seen in Figure l5.

The groove 162 terminates at 167 forming. ay stopy shoulder to` Yengage the ball v164 eliminatingthe outward movement of the piston 138 in the bore 118. The

bore 144 is communicated with the bore 139 in the piston 138 by a relatively short bore 168.

A cylindrical piston 169 is positioned in the bore 139 and adapted for vertical reciprocation therein. The piston 169 has an annular groove 170 formed adjacent the lower end thereof containing an elastic seal 171. The lower end of the piston 169 has an annular groove 172 on the peripheral edge thereof and a circular groove 173 positioned concentrically inwardly of the groove 172. An elastic sealing ring 174 is positioned in the groove 173 for engagement with the lower end of the bore 139.

A vent bore175 extends upwardly from the annular Y groove 172 through the upper end of the piston 169 and has its upper end closed by a conventional bleeder valve 176. An elongated groove 177 extends upwardly along the outer face of the piston 169 from a point spaced above the lower end thereof outwardly through the upper end thereof. The lower end of the groove 177 terminates in a shoulder 178.

The bore 13 9 of the piston 138 has ay groove 179 extending downwardly from the upper edge thereof and a ball 180 is seated in the grooves 177, 179 for engagement with the shoulder 178 to secure the piston 169 in the bore 139. An L-shaped member 181 is positioned in the groove 179 and secured to the piston 138 by meansof a bolt 182 to retain the ball 180 in the groove 179.

The piston 169 has an axial bore 183 extending therethrough to a point adjacent to but spaced from the lower end of the piston 169. An upstanding hollow boss 184. is formed centrally of the piston 169 atV the lower end of the bore 183 and has a valve seat 185 formed therein.

A valve 186 is associated with the valve seat 185 and has a stem 187 extending downwardly therefrom through the orice 168. A coil spring 188 is positioned within the hollow boss 184 engaging at one end the valve seat An elongated piston 190 is arranged for reciprocation in the bore 183 and has an elongated slot 191 formed in the outer face thereof and terminating at its lower end i in a shoulder 192. A groove 193 is formed in the bore 193 extending inwardly from the upper end thereof and a ball 194 is positioned in the groove 191 and the groove 1,93 where it is retained by an L-shaped member 195 secured to the piston 169 by a bolt 196. I

The shoulder 192 engages the ball 194 to limit the outward movement of the piston 190 in the bore 183. The piston 190 has an annular groove 197 adjacent the lower end thereof and containing a sealing ring 198 for engagement with the bore 183. l

A bore 199 extends upwardly from the lower end of the piston 190 to receive the hollow boss 184 therein. An elongated vent bore 288 extends from the bore 199 through the upper end of the piston 19t) and is closed at its upper end by a conventional bleeder valve 201.

:A circular plate 202 is secured to the upper end of the piston 190 by welding or the like and has a diameter equal to the body 117. A pair of coil springs 203 have their upper ends connected to pins 204 to the plate 282 and their lower ends mounted over pins 285 projecting outwardly from the body 117. The springs 283 are artool great for the piston 190, the pressures in'the jack 116 increase due to the piston 190 stopping its movement with respect to the bore 183.

As Vthe pressures increase, the valve plug 147 overcornes the resistance of the spring 146 and movesoutwardly away from the Valve seat 148 and simultaneously aligns the annular groove 151 with the valve stem 187 so that the valve 186 can close against the valve seat 185 sealing the bore 183 to prevent the piston 198`from moving downwardly therein.

Additional iiuid pressure exerted on the hydraulic uid will cause the hydraulic uid to flow through the restricted passage 152, the bore 153, into the annular groove 172 so as to raise the piston 169 in the bore139. The piston 190 is locked by the valve 186 to the piston 169 so that movement of the piston 169 will cause the piston 190 to move therewith with the increased force brought about by the increased cross-section of the piston 159 Y over the piston 190.

.When the piston 169 has moved to 4fully extended posi.- tion, locking the shoulder 178 to the ball 180, the fiuid pressure in the bore 139 working on the piston 169 will move the piston 138, then locked to the piston 169, off its seat in the bore 118 and will allow valve stemi159 to leave its seat on the bottom of the bore 121i. Spring 160 will then close the valve 158 and simultaneously with the lifting of the piston 138 and the closing of the valve 158, uid pressure will ow by the seal 122, into the bores 118 and 128. ri`hereby, the piston 138 will continue to carry the load to the desired distance. Having the piston 138 go into operation only after the piston 169 has traveled to fully extended position covers that phase in my invention of multiple nested piston devices which is to produce a lifting or moving hydraulic device that will lift or move an object a greater distance than any hydraulic device ofk equal length, Yknown to Should the pressure of the hydraulic uid in the bore 118 exceed the capacity of the jack 116, the ball valve 135 will be unseated and the iiuid will ow through the bore 134 and bore 128 to the conduit 132, returning to the reservoir (not shown).

In lowering the jack 116 to the position illustrated in Figure l5, hydraulic pressure is removedfrorn the hydraulic fiuid within the jack 116 and pistons V190, 169

and 138 will lower as a unit until the piston 138 is completely housed within the bore v118and the stem 159 contacts the bottom of the recess 120 to raise the valve 158 off ofthe valve seat 157 and release the uid trapped in the bore 139.

When the valve 158 opens, the piston 169 moves downn wardly until the stern 187 contacts the valve plug 147 position.

ranged parallel to the axis of the body 117 and are adapted to move the plate 202 downwardly upon the s until the work to` be lifted is, contacted, and if, the. lpad is' Referring now to Figures 16 and 17, Vanother modified form of the invention is illustrated comprising a wheel cylinder indicated generally at 206. The wheel cylinder 206 includes a generally cylindrical body 207 having axial bores 2li-8 extending inwardly from opposite ends thereof and terminating at a central transverse partition 209. The partition 209 has oppositely extending rings 210 projecting into the base of the bores 208.

An axial bore 211 extends through the partition 209 communicating the bores 208 on opposite sides thereof, vand a fiuid port 212 communicates with the bore 211 to supply hydraulic iluid under pressure to the bore 211.

A second bore 213 parallel 'to the bore 211 extends through the Battiti@ 20.9 @menuiseries the bones21@ 'atithe "sides thereof. A port 214 communicates with the'bore 213 at-one end and has the opposite end thereof connected to the same source of fluid pressure (not shown) to which the port 212 is connected.

A piston 215 of cylindrical cross-section is arranged for reciprocation in each of the bores 208 and is provided with a reduced cross-section axial extension 216 having a slot 217 in the outer end thereof for engagement with the opposed ends of brake Yshoes 218. The pistons 215 have vaxial bores 219 extending therein from the outer end thereof. f

An offset bore 220 extends through the pistons 215 at the bottom of the bores 219 and is provided with a valve seat 221 on the side thereof next to the bore 219. A valve 222 is arranged for cooperative engagement with the valve seat 221 and has a stem 223 extending through` the bore 220 and arranged for engaging the partition 209.

yA coil spring 224 is arranged in engagement with the inner end of the piston 215 at one end and has the opposite end engaging a collar 225 xed to the stem 223. The spring 224 normally biases the valve 222 into engagement with the valve seat 221 and engagement of the stem 223 with the partition 209 raises the valve 222 out of engagement with the seat 221 when the pistons 215 are in their innermost position.

The pistons 215 each have a cylindrical boss 226 extending inwardly thereof and over which resilient sealing cups 227 are engaged. Y

A coil spring 228 is positioned in engagement with the outer end of the pistons 215 encompassing the reduced end portion 216 thereof and have their outer ends engaging a snap ring 229 seated in a groove 230 formed in the outer end of the bore 208. i

A cylindrical piston 231 is arranged for reciprocation in the bores 219 and is provided with a slot 232 at its outer end for engagement with the brake shoes 218. A flexible sealing cup 233 is positioned in engagement with the inner'end of the pistons 231 and in sealing engagement with the bores 219.

In the use and operation of the invention illustrated in Figure 16, fluid pressure enters the Wheel cylinder 206 through the port 212, bore 211, into the bore 208, through the bore 220, past the valve 222 into the bore 219. As thehydraulic Huid, under pressure, enters the bore 219 the'piston 231 is forced outwardly in the bore 219 until the brake shoes 218 are in engagement with the brake drum of the vehicle wheel (not shown).

As thebrake drum stops the outward movement of the piston 231, the pressure of the hydraulic lluid will enter the bore 208 through the port 214 as Well as the port 212, and will act on the pistons 215 to move them outwardly away from the partition 209. As soon as the pistons215 move away from the partition 209, the stems 223 leave the partition 209 and the springs 224 close the valves 222 locking the uid in the bore 219 and holding the pistons 231 in their extended position.

Further pressure applied to the hydraulic uid will move the pistons 215 outwardly to apply a pressure to the brake shoes-218 far in excess of the pressure applied by the piston 231.-

When the pressure is released on the hydraulic fluid, the springs 228 return the pistons 215 toward the partition 209, and as'they reach their innermost position,

the lstems '223' engage the partitions 209 opening the valve 222 to release the trapped fluid from the bore 219 and permit the pistons 231 to be returned to their retracted l0 what larger bore `239 vented at 239a communicates therewith and extends axially through the body 235.

A threadedA bore 240 extends through the end of the extension 237 communicating with the bore 238' and is closed by a conventional bleeder valve 241. A conduit 242 is connected to a threaded bore 243 in the end of the extension 237 by means of a threaded fitting 244. An arm 245 connects the bore 238 to the bore 243.

A cylindrical block 246 has a diameter equal to the diameter of the ange 236 and isv secured thereto by mounting bolts 247. The block 246 has a transverse bore 248 extending therethrough and is provided with a threaded outer .end portion 249 in which is mounted a threaded bushing 250.

An adjusting stern 251 is journalledin the bushing 250 and has a collar 252 formed intermediate the opposite ends thereof and engaging the bushing 250 to secure the shaft 251 against outward movement therein. A threaded extension 253 extends inwardly from the shaft 251 and its inner end serves as a stop for a valve plug 254 arranged for reciprocation in the bore 248.

A plate 255 is threadedfon the threaded extension 253 and has oppositely disposed ears 256 engaged in slots 257 in the side of the bore 248 to prevent the plate 255 from rotating with respect to the bore 248. A coil spring.258 is interposed between the plate 255 and the valve plug 254 to normally bias the valve plug 254 into engagement with a valve seat .259 formed at the inner end of the bore' 248. l y

A longitudinally extending bore 260 communicates with vthe valve seat`259 and with a threaded bore 261` normally closed by a conventional bleeder valve 262. The block 246 is provided with an annular groove 263 having an outer diameter equal to the bore 239 and communicating therewith. The bore 260 communicates with the groove 263.

A second annular groove v264 is formed on the block 246 in surrounding relation to the groove 263 and has a resilient seal 265 positioned therein and engaging the flange 236 to seal the block 246 to 'the body 235.

A bore 266 extends between the bore 248 and the l 'bore 239, and the block 246 is provided with an annular engaged in the bore 239 and having an annular groove 276 formed therein to receive a sealing gasket 277 engaging the walls of the bore 239 to seal the piston portion 275 thereto. i

'The piston member 274 has a second piston portion 278 having a diameter to permit sliding movement thereof in the bore 238. The piston portion 278 has'an annular groove 279 adjacent its outer end in which is positioned a sealing ring '280 for sealing engagement with the bore The piston portion 275 has a bore 281 extending inwardly thereof and the piston portion 278 has a bore 282 extending inwardly thereof with the bores 281 and 282 being axially aligned and communicated by a bore 283 extending therebetween.

The end of the bore 283 adjacent the Vbore 282 is pro vided with a valve seat 284 closed by a valve 285.Y The valve'y 285 has a valve stern 286 extending through theV bore 283, through the bore 281, and through the bore 266.

A guide collar 287 is fixed to the stem 286 and is provided with orifices 288. A coil spring 289 is positioned in the bore 281 engaging the inner end of the bore 281.

at one end and the collar 287 at the other end to normally bias the valve 285 into` contact with the valve seat 284.

A coil spring 290 engages the inner end of the bore 239 at one end and the piston portion 275 at the other end to normally bias the piston member 274 toward the block 246.

In the use and operation of the invention illustrated in Figure 18, hydraulic iluid under pressure is delivered to the pressure multiplying device 234, through conduit E?,

272, into bore 248, through bore 266, into bore 281, through the oriiices 288, borey 283, past the Valve seat 284, into the bore 282, and the bore 238.

Hydraulic duid continues to flow under pressure through the conduit 272 until the bore 238 is completely lled,

and the Huid extends under pressure completely through the conduit 242 to the device (not shown) to be actuated thereby.

As the pressure increases in the pressure multiplying device 234, the valve plug 254 is forced downwardly against the tension of spring 258 aligning an annular groove 291 therein with the stem 286 so that the spring 289 can force the stem 286 in a direction to close the valve 285 against the valve seat 284 and lock the uid in the bores 238, 282 and conduit 242 from returning to the bore 281.

After the valve plug 254 has moved downwardly in the bore 248, fluid flows through a greatly restricted boreV to the uid trapped in the bores 282, 238 and the conduit 242 greatly in excess of the pressure in the conduit 272 acting on the piston portion 275.

On release of the pressure in the conduit 272,'the valve plug 254 is pressed upwardly by the spring 258 so as to contact the seat 259 and seal the bore 292 and simultaneously move the annular groove 291 out of alignment with the stem 286.

The pressureA of the spring 290 returns the piston member 274 to its starting point inthe bore 239, and as it reaches its innermost position the stem 286 contacts the Y valve plug 254 and causes the valve 285 to unseat from the valve seat 234 to release the hydraulic uid in the bore 282, bore 238, and conduit 242, returning all of the elements of the device to normal.

Having thus described the preferred embodiments of the invention, it should'be understood that numerous other structural modifications and adaptations may be resorted to without departing from the scope of the appended claims.

What is claimed is:

l. A hydraulic device comprising a hollow cylinder, a hollow piston mounted for reciprocation in said cylinder, a second piston mounted for reciprocation in said iirst piston, means for connecting said cylinder to a source of fluid under pressure, seal meansffor separating said iluid under pressure from a large area of said hollow piston, a valved port extending through said hollow piston and communicating with the means connecting said cylinder to a source of fluid under pressure, and means actuated by fluid under pressure in said cylinder for initially maintaining said seal means in sealed condition` and for initially maintaining said valved port in open con ydition to permit the iluid under pressure to move said second piston outwardly in said hollow piston and said last named means to move under iluid pressure in said cylinder to a position permitting the opening of said seal means `and the closing of said valved port locking the fluid in said hollow piston and directing the uid under pressure against the large area of the hollow piston to move said hollow piston outwardly in said cylinder.

2. A devicefas claimed in claim l wherein said valved port is closed by a reciprocating valve having a valve` stem engageable with the means for maintaining said valved port in open condition, whereby said valved port is closed prior to movement of said hollow piston.

3. A device as claimed in claim 1 wherein the means for maintaining said valved port in open condition and maintaining said seal means in sealed condition includes a reciprocating valve plug movable under fluid pressure to close said valved port prior to movement of said hollow piston.

4. A hydraulic device comprising a cylinder, a plurality of coneentrically arranged hollow pistons mounted for reciprocation in said cylinder, means connecting said cylinder to a source of hydraulic fluid under pressure, means for conducting said hydraulic uid to move the innermost of said pistons with respect to the remainder of said pistons, sealing means for separating the remainder of said pistons from the fluid under pressure, means responsive to fluid under pressure for Vautomatically and simultaneously locking the iluid under pressure behind said innermost piston in its extended position and directing the uid pressure against a next larger piston, means for mechanically locking said next large piston in fully extended position whereby said uid under pressure directed against the next larger piston will move the piston in which said next larger piston reciprocates, means for directing said hydraulic iluid against the piston in which said next larger piston reciprocates, and means for locking fluid under pressure behind said fully extended next larger piston whereby the fluid under pressure in the cylinder is directed solely against said piston in which said next larger piston reciprocates,

5. A device as claimed in claim 4 wherein said means responsive to fluid under pressure in said cylinder is provided with means Lfor locking said Huid under pressure behind said innermost piston in extended position prior to a movement of said next larger piston.

References Cited in the le of this patent UNITED STATES PATENTS` 1,865,105 Houplain June 28, 1932 2,227,245 Carroll Dec. 31, 1940( 2,282,556 Bowen May 12, 1942 2,389,654 Van Der Weri Nov. 27, 1945 2,597,404 Teske May 20, 1952 2,638,750 Hettinger May`l9, 1953 2,649,691 Johnson Aug. 25, 1953 2,737,777 Krusemark Mar. 13,` 1956 FOREIGN PATENTS l Y 905,934 Germany Mar. 8, 1954 

